1. Field of the Invention
The present invention generally relates to an illumination lamp, and particularly to a lamp cover of the illumination lamp.
2. Description of Related Art
In recent years, light emitting diode (LED) as a highly efficient light source is widely used in such fields as automobiles, display screens, and traffic lights.
FIG. 9 shows a simulated view of a light field of the LED. The light field of the LED is approximately circular. An intensity of the light field of the LED gradually decreases outwardly along a radial direction. Thus, the light field intensity near the LED is higher, and the light field intensity far from the LED is lower. However, in some cases, when the LED is adopted for a street lamp, the shape of the circular-shaped light field is often different from that of the street. As a result, a lighting area of such LED projected on the street is small. Thus, more LEDs are required for lighting the street, resulting in high cost and inefficient of energy.
FIG. 10 shows a light field of a street lamp 20 using LEDs as light source. The street lamp 20 is always positioned at one side of a street 22. Because of the circular-shaped light field of the LED, some of light emitted from the LEDs only covers a portion of the street 22. Thus, the street lamp 20 has a low utilization efficiency of the light emitted from the LEDs.
For the foregoing reasons, there is a need in the art for an illumination lamp which overcomes the above-described shortcomings.